Introduction

The source of the majority of the information contained in this FAQ
has been extracted from various technical sources, discussions with
local mechanics, and postings to The Saab Network. Since so any
people have contributed to this topic in The Saab Network
Archives, it proved impractical to give credit to all the appropriate
individuals. This is in NO way the definitive answer on how to
perform the procedure. Rather, it is the summation of several
different sources of information in an attempt to provide a resource
for people to draw upon when attempting to perform a repair
themselves. The suggestions given are intended to enhance your
general understanding of your car's operation. The repairs suggested
and the methods described, though they may have worked for others,
may or may not work for your car due to variations in models,
equipment, and other unknown factors. When all else fails, you can
take your car to your trusted local SAAB mechanic and have them
do the repair for you.

This is intended to be "living" document, so, if you see something
that is incorrect or you can add to the topic, send me an E-mail
(Kevin Yankton)
and I'll do my best to address it.

Neither I nor Applied Materials, Inc. assumes responsibility for the
accuracy of the information contained here.

Having said all that...

General Information

I have found that fixing the fuel injection system is not some sort of
black art, but a logical progression of mechanical and electrical checks,
each of which produces more information to tell you what is right and
what isn't. To that end, if you approach any job on your Saab in a logical
way and understand how the systems function, you can understand what
is malfunctioning and avoid the shotgun approach to car repair (which
can end up costing the shade tree mechanic more than if the car was
taken to a qualified Saab mechanic in the first place).

Overview of L/LH-Jetronic Fuel Injection Systems

The Bosch L-Jetronic and LH-Jetronic (Luftmassenmesser Hitzdraht) is
a pulsed injection type system. In pulsed injection, all air entering the
engine first flows through an air-mass meter. The air-mass meter
measures the air, which indicates engine load, and converts that
measurement into an electrical signal to the control unit (ECU). The
LH-Jetronic is a fuel injection system, not an engine management system.
While most L-Jetronic cars have electronic ignition, they do not have
electronic management of ignition timing.

Beginning in about 1980 (earlier in California), Lambda (oxygen sensor)
control was added to the system in an effort to reduce exhaust emissions.
The LH-Jetronic is a further refinement of the L-Jetronic in that the LH
used an air mass meter as opposed to the air flow sensor of the L. The
early LH 2.2 fuel injection system is on the '85 through '88 16 valve
turbo engines and '86-'87 normally aspirated 16 valves. These systems
can be identified by the metal air mass meter with an idle mixture screw,
a dashpot (damper) deceleration control for the throttle lever, and an AIC
idle control valve with a three wire plug. The LH 2.4 and 2.4.2 systems
are identified by the black plastic air mass meter and a two wire AIC
valve. While the harness may be the same for both types of air mass
meters, these should NEVER be swapped as they are not identical.
Swapping them will most likely result in having to replace the air
mass meter.

The deceleration function was moved to the ECU in the 2.4 system. The
dashpot was designed to provide a controlled deceleration to 875 rpm in
3 to 6 seconds from an engine rpm of approximately 3,000.

The two engine conditions which make a primary contribution to the
basic flow rate are load and speed. Additionally, compensation
variables (such as starting, cold operation, and special load conditions)
and precision compensation variables (tweaking the other compensations
for overrun or coasting and mixture control for emission reduction) are
added to, or subtracted from the basic flow rate to achieve smooth
operation. Cold start can pose a special problem because the fuel does
not properly vaporize and even if it is adequately vaporized, some fuel
condenses on the cold parts of the engine before it can be burned. In cold
start conditions, the engine requires extra fuel for starting so that, in
spite of vaporization and condensation problems, the engine still receives a
combustible air-fuel mixture.

In measuring the volume of the air passing through the intake manifold into
the engine, the air-mass meter provides a measure of engine load. Engine
speed is measured in the tachometer by counting the ignition pulses in the
primary circuit. The LH-Jetronic rpm signal comes from the primary ignition
pulse, the current that turns the coil on and off. For most cars that is a
signal which comes from the negative terminal of the ignition coil.

ECU Function

The ECU receives information from the following sensors:

The ignition system provides information on engine speed.

The temperature sensor provides information on the temperature of the
engine coolant.

The throttle position switch provides information on the position of the
throttle butterfly. In the LH 2.4.2 system, the switch is replaced
by a potentiometer sensor.

The air mass meter provides information of the air mass supplied to
the engine.

The oxygen sensor provides information on the oxygen content of the
exhaust gases.

The speed sensor provides information on the speed of the car.

Ignition System and Ignition Timing

All the testing should also be based on the fact that the other systems,
including the ignition, are in proper working order (after all, these are
relatively inexpensive fixes). The plugs should be gapped at 0.024"-0.028"
(0.6-0.7 mm) and tightened to a torque of 20.7 ft-lbs. (28 NM). The plug
wires should be checked to assure that resistance is within 2,000 to 4,000
ohms. Inspect the distributor cap and replace it if the contacts are burnt
or tracer lines are apparent. Measure rotor resistance (1,000 ohms) and if
it is out of range or the contact is burnt, replace it by breaking off the
old rotor and pressing the new one in place with the appropriate glue (Loc
Tite seems to work well).

Any testing of the ignition system would be incomplete without also checking
the timing. Since there are different settings for different models,
markets, and years, you should be able to find the correct timing for your
car by checking the sticker on the fender. Ignition timing is measured at
the instant the spark plugs fire, in terms of degrees of crankshaft rotation
relative to the piston on its compression stroke and before or after top
dead center. When the engine is idling, the spark is timed to occur just
before the piston reaches top dead center so that combustion can be
completed by the time the piston reaches a little past top dead center. At
higher engine speeds, there is less time for the air/fuel mixture to ignite,
burn, and deliver its power to the piston. Consequently, at higher engine
speeds, the spark must be delivered earlier in the cycle.

To check your timing, the first thing you are going to need is a strobe
timing light. The induction pick-up should be attached to the number one
plug wire. On the 900, the number one cylinder is at the firewall end of
the engine and on the 9000, it is opposite of the distributor. If you still
can't figure it out, pull the spark plug inspection plate and read the
cylinder number stamped by each plug on the head.

When pistons number one and number four are at top dead center, the
crankshaft (i.e., the '0' mark on the flywheel) will be in line with the
mark on the clutch cover or end plate if the clutch cover has been removed.
Disconnect the vacuum control hose at the vacuum chamber on the distributor
and plug the hose (this allows for a true base timing reading). Loosen the
distributor tightening bracket bolt. Focus the light of the timing light
strobe on the flywheel. The rotation of the flywheel and the pattern of the
strobe light will indicate the current timing setting. If your timing light
has an advance setting, you will target a '0' mark on the flywheel. If you
do not have an advance, you will target a setting equivalent to your car's
specific timing advance setting. The mark on the flywheel should hold
steady (within 1-2 degrees) and not bounce around. If it does bounce
around, this is an indication that something is wrong (possibly the
distributor). You should also test that the vacuum advance is working by
applying vacuum to the distributor.

Under light engine load conditions, there is a high vacuum in the intake
manifold caused by the restriction of the partially closed throttle valve.
Consequently, there is a smaller amount of air/fuel mixture delivered to the
combustion chamber. Because of the lower ratio of fuel to air, the mixture
will not burn as rapidly; therefore, ignition must take place early in the
cycle.

To provide additional spark advance control based on intake manifold
pressures, a vacuum advance mechanism is incorporated in the distributor. It
contains a spring-loaded diaphragm which rotates the breaker plate assembly
in the distributor. The vacuum diaphragm is connected to the intake
manifold. When the engine is at idle, intake manifold vacuum is high and
the ignition timing is advanced. When the engine is accelerated, intake
manifold vacuum drops, retarding the ignition timing of spark plug firing.

Engine Temperature / NTC Sensor

One of the least known sensors is the engine temperature sensor
(aka NTC II). It is a semiconductor resistor, also know as a thermistor,
and the NTC stands for Negative Temperature Coefficient. This means
that the sensor's resistance goes down as the temperature goes up. If the
ECU applies a fixed voltage to the NTC resistor, it will receive a smaller
signal back as input from a cold resistor with higher resistance than from
a warm one. This sensor is screwed into the water passage on the intake
side of the head between intake runner #2 and #3 on the 900s and just
under runner # 2 on the 9000s. Test the sensor by probing the two
contact points with a multimeter to measure the resistance which
should be:

Cold Engine -5,800 ohms @ 32F (0C) to 2,600 ohms @ 68F (20C)

Warm Engine - 320 ohms @ 176F (80C) to 180 ohms @ 212F (100C).

Throttle Body and Switch

A dirty or gummed up throttle body can contribute to an erratic idle
situation. This can easily be cleaned once or twice a year. Cleaning it
only requires that you remove the intake hose to the throttle body and move
it out of the way. To prevent any unwanted items from falling in the intake
hose, it should be blocked with a clean rag. Using a can of carburetor
cleaner, open the throttle butterfly with one hand and spray cleaner just
beyond it. Wipe out any gunk that is preventing the butterfly from
operating properly.

The throttle position switch provides the ECU with information on the
position of the throttle: idling speed, partial throttle, or wide open
throttle. In the LH 2.4.2, the position switch is replaced by a throttle
position sensor. The switch has three pins of which the center provides the
ground connection. When the throttle is closed (idling speed or engine
braking), the microswitch closes and ground is obtained from the idling
speed connection/pin. When the throttle is activated, the microswitch opens
and the ground from the idling speed connection/pin is lost. When the
throttle angle is greater than 72 degrees, the wide open throttle switch
closes and ground is obtained from the full-load pin. After an ECU
calculation is performed, full-load enrichment is provided to the fuel-air
mixture. (See the FAQ on Adjusting Basic Idle)

If the accelerator is floored when the engine is started at temperatures
below -4F (-20C), the ECU issues an order to reduce the amount of fuel
injected into the engine. This prevents the engine from becoming flooded.
In the LH 2.4, 2.4.1, and 2.4.2 only, repeated attempts to start the engine
will cause the enrichment cycle to not be activated. This prevents
exceptionally generous enrichment and a consequently flooded engine.

Idle Air Control Valve

From model year 1986 and later, the auxiliary air valve is replaced by
an idle air control valve (AIC) which also compensates for momentary
load increases at idling speed. The AIC is bolted to a bracket mounted
on the intake manifold. The valve allows a controlled flow of air to
bypass the throttle butterfly. The volume of the air is determined by
the degree of opening of the idle control valve. The AIC consists of a
slide valve with a reversible motor. The motor has two windings and
maintains a continuous reciprocating action, turning the slide through
a maximum angle of 90 degrees. The motor receives signals from
the ECU.

Due to the AIC motor's continuous, limited-travel reciprocating action
(noticeable only as vibration), the opening of the valve can be varied
within extremely short periods of time (opening/closing in about
150-200 milliseconds). This permits the air flowing through the valve
to be controlled at all times so that the volume necessary for obtaining
the desired constant or increased idle speed can be achieved as required.

The AIC for the LH 2.4, 2.4.1, and 2.4.2 differs from the LH 2.2 in that the
reversible motor is replaced by a solenoid. The coil receives pulse signals
from the ECU. When activated, the coil overcomes a mechanical spring that
keeps the valve closed. This allows a specific volume of air to flow past
the throttle butterfly in the intake manifold. In the event of a fault, the
opening pulses terminate and the spring pulls the valve to the end position.
The air flow through the valve in this position (Limp Home) is greater than
during normal operating conditions. This gives an idle speed of 1,200 to
1,500 rpm.

Air Mass Meter

The air mass meter is usually mounted some distance from the intake
valves rather than directly on the engine manifold. Any air that enters
the intake system between the meter and the valves is UNMEASURED
AIR. Therefore, the engine gets no fuel to match that air. The result
can be lean mixtures that can cause hard starting, rough idle, low CO,
and stumbling. This is why people always say to check for any vacuum
leaks first as this is relatively easy compared to some of the other test
procedures and you may find your problem right away. Additionally,
turbos have a bad habit of blowing these hose connections apart under
high boost.

The air mass meter depends on the measurement of current flowing
through heated wires to measure air flow. It is also known as the
hot-wire sensor because of its heated wire design, hence the "H" in LH.
In the unlikely event that a wire should break, the warm engine runs,
though without fuel compensation, in a "Limp-Home" mode. For
"Limp-Home" operation, injector pulse time is fixed. For any rpm
above idle, the ECU is programmed to deliver fixed pulses,
typically 7.5 milliseconds.

The air mass meter works by measuring the air mass, or weight, so it
requires no correction for changes in density due to temperature or
altitude. The hot wire system depends on the measurement of the
cooling effect of the intake air moving across the heated wires. With a
small movement of air past the heated wires, the cooling effect is small.
With more air moving past the heated wires, the cooling effect is greater.
LH control circuits use this effect to measure how much air passes
the LH hot wire.

The LH hot wire is found within the air passage tube of the air mass
meter and is made of a platinum filament. The hot wire is heated to a
specific temperature differential above the incoming air when the
ignition is turned on (the differential is measured in degrees Celsius).

LH 2.2, aluminum: 212F (100C)

LH 2.2 and LH 2.4, plastic: 248F (120C)

LH 2.4.1 and 2.4.2, plastic: 311F (155C)

As soon as the air flows over the wire, the wire is cooled. The control
circuits then apply more voltage to keep the wire at the original
temperature differential (100 degrees C). For example, if the air is at
freezing, 32F (0C), the wire will be heated to 212F (100C). On a hot day,
if the air is at 86F (30C), the control circuits heats the wire to the same
212F (100C) difference to 266F (130C). This creates a voltage signal which
the ECU monitors - the greater the air flow and wire cooling, the greater
the signal. These signals are transmitted from the air mass meter to the
ECU as follows:

up to model year 1987 (non-Turbo) and up to model year 1988 (Turbo )
from pin 5 (air mass meter) to pin 7 (ECU).

from model year 1988 (non-turbo) and from model year 1989 (Turbo)
from pin 3 (air mass meter) to pin 7 (ECU).

Since the filament is located in the inlet duct, it becomes dirty and loses
its sensitivity over time, which affects measurement accuracy. To ensure a
clean sensor, the control system will heat the wire red hot for about one
second, hot enough to burn-off any dirt. However, there is no burn-off
unless the engine has run above 3000 rpm and attained a engine temperature
of 150F (65.6C). This burn-off function takes place 20 seconds (4 seconds
for the LH 2.2) after the engine has been switched off.

Vacuum and Related Sensors

Vacuum leaks can be caused by any loose clamp or gasket, or by any slit in
the flexible intake hose or vacuum hoses. The vacuum hoses are the small
black hoses running from various ports on the manifold to points on the
engine such as the fuel pressure regulator, the crankcase vent fitting
and/or valve, the distributor vacuum control, heater control vacuum tank,
the fuel evaporation control canister, the "hooter" valve, etc. The
crankcase ventilation system evacuates crankcase gases through the throttle
body.

The "hooter" valve is notorious for leaking vacuum, however, it is a very
easy item to test. Test it by connecting a vacuum hose to the nipple and
draw a vacuum. If it holds, you are good. If it looses vacuum, it needs to
be replaced. The purpose of the "hooter" valve or officially known as the
turbo bypass value is to shunt excess turbo boost pressure when the throttle
is suddenly closed. The "hooter" valve can upset idle by allowing bypass
air into the intake manifold and interfering with vacuum at idle.

Oxygen / Lambda Sensor

The lambda sensor (aka oxygen sensor) is essentially a small battery that
generates a voltage signal based on the differential between the oxygen
content of the exhaust gas and the oxygen content of the ambient air. The
tip of the sensor that protrudes into the exhaust gas is hollow, so that the
interior of the tip can be exposed to the ambient air. Both sides of the
ceramic tip of the sensor are covered with metal electrodes that react to
create a voltage only if the ambient air has a higher oxygen content than
the exhaust and the ceramic material is hotter than 575F (300C). The
electrolyte consists of a ceramic material, zirconium oxide, which has been
temperature stabilized through the addition of a small amount of yttrium
oxide. The electrolyte is in tubular form with one of the ends blanked off.
The surface has been coated with platinum to make it electrically
conductive.

The voltage is usually about 1 volt, but if the engine is running lean, the
exhaust gas has about the same amount of oxygen as the ambient air and the
sensor will generate little or no voltage. If the engine is running rich,
the oxygen content of the exhaust will be much lower than the ambient air
and the sensor voltage will be larger. Sometimes the voltage reading is
disturbed by a poor ground situation due to corrosion. To test for a poor
ground, connect a 12V bulb to the oxygen sensor body and the battery
positive. The bulb should light up indicating current flow and a good
ground. If it does not light up, remove the oxygen sensor and clean the
threads. Alternatively, you can run an extra ground lead from the oxygen
sensor's outer casing (secured with a hose clamp) to a good engine ground.
Resistance for preheating is 4 ohms, + or -2 ohms (at 20C/68F). To check
this, unplug the electrical connector (square, two pin connector) and use a
multimeter to check the resistance across the oxygen sensor terminals.

Fuel Delivery System

The LH-Jetronic is a re-circulating fuel system in that the electric fuel
pump delivers more fuel than is needed even at full throttle, so most of
the fuel is returned to the tank. This design essentially eliminates the
condition know as "vapor lock" (vaporized fuel in the lines) since the
fuel temperature is kept low by constant re-circulation and reducing the
heat-soak from the hot engine compartment. Additionally, the fuel pump
is typically located in or near the tank so that the maximum length of the
fuel lines are pressurized, usually about 2.5 bar (36 psi), to reduce vapor
lock. Vapor lock is the situation where, unlike liquid fuel, vaporized
gas becomes trapped in the fuel lines (compressible) and the fuel pump
cannot necessarily overcome the problem and deliver fresh fuel.
Another point with this type of system is that you should not run the car
for extended periods with a low tank of gas. The reason being that the
fuel acts to cool the fuel pump. So, if you do run out of gas, just don't
crank a long time or you may ruin the pump.

Fuel Rail and the contribution it makes

Another part of the fuel delivery system is the fuel rail. Other than being
a source for fuel delivery, it serves to stabilize fuel pressure at the
injectors. You can imagine how the pressures change rapidly in the fuel
rail as the injectors pop open and closed. This can affect the amount of
fuel injected. But the larger the fuel rail (usually a square box shape),
the more fuel it stores and the steadier the pressure at the injectors. In
smaller pipes, with small volume, pressure tends to fluctuate each time the
injectors open.

Fuel Pressure Regulator

The relative fuel pressure in the fuel system is held constant by the
pressure regulator. The design of the regulator is that spring pressure
normally keeps the regulator valve closed. When the fuel pumps turns
on, fuel pressure presses on the diaphragm to compress the spring and
opens the valve, returning excess fuel to the tank. The higher the
pressure, the more the diaphragm moves away from the return pipe,
increasing the volume of the chamber, maintaining the desired pressure.
Most systems operate on 2.5 bar (36 psi) gauge pressure, but some people
have installed the 3.0 bar (44 psi) for greater fuel delivery per
millisecond. For the 9000, standard fuel pressure regulators were as
follows: pre-'86 Turbo-2.5 bar (36 psi), post-'87 Turbo-2.8 bar (40 psi),
non-Turbo B202I '86 on and B234 '90 on use the 3.0 bar (44 psi).

For each millisecond of injector pulse time, the amount of fuel delivered
through the injector tip depends on the size of the injector opening: that's
a fixed factor. But fuel delivery also depends on the relative pressure -
the difference between fuel pressure pushing the fuel out into the manifold
and manifold absolute pressure pushing back. As you can imagine, the
manifold pressure changes when the throttle opens. If the fuel pressure
were constant for all manifold pressures, then at low engine loads, with the
throttle partly closed, reduced manifold absolute pressure would increase
fuel delivery. To keep that relative pressure constant as the throttle is
opened and closed, the fuel pressure regulator is connected to the intake
manifold by a vacuum hose. Manifold pressure acts on the diaphragm to hold
the relative pressure constant.

At full throttle, manifold pressure is close to barometric, so the fuel
pressure gauge reads about 2.5 bar. At idle, absolute pressure in the
manifold is about 0.3 bar (0.7 bar less than barometric). Now the manifold
absolute pressure pushing the pressure regulator diaphragm is only 0.3 bar
instead of 1 bar. The reduced manifold pressure on the diaphragm allows it
to move away from the opening, returning more fuel to the tank, and dropping
the gauge fuel pressure in the distributor pipe to about 1.8 bar (2.8
absolute). The relative pressure at the injector tip is still 2.5 bar (2.8
minus 0.3 absolute). That's why fuel delivery per injector is not affected
by changes in the manifold absolute pressure.

Manifold Pressure

While we're on the topic of manifold pressure, we should also consider
the information conveyed by reading a manifold vacuum gauge. First
you need a good quality, large dial vacuum gauge (I got one made by
Actron which cost me less than $20). This gauge can be connected into
most any vacuum hose that normally connects to the intake manifold.

Before we get into the actual testing, we should probably take a moment
to discuss how vacuum is generated and how it is measured. Put simply,
vacuum is empty space and may exist as either a total or partial vacuum.
The atmosphere exerts a pressure of 14.7 pounds per square inch (psi) or
1 bar on everything at sea level. If a part of the air is removed from one
side of a diaphragm (partial vacuum) then a force is equal to the pressure
difference times the diaphragm area. Generally, the less air (greater
vacuum) in a given space, the more the atmosphere tries to get in and
the more force is created.

Vacuum is commonly measured in either inches ("Hg) or centimeters
(cm Hg) of Mercury. Atmospheric pressure will support a column of
Mercury in a manometer gauge about 30" high or about 76cm. This is
the barometric pressure in "Hg which varies as the weather changes.
Vacuum readings in "Hg are really negative pressure readings. For
example, 30"Hg vacuum would be a complete vacuum. Half of a
complete vacuum would be about 15"Hg. A gasoline engine at idle
usually pulls about 16" to 22"Hg of vacuum in the manifold. On
deceleration, because the throttle is closed, the vacuum will increase.

As noted above, vacuum is created when air is withdrawn from a given
volume. That, of course, is why vacuum is available in an engine. On
the intake stroke, the piston moves down and creates a partial vacuum
because the volume of the cylinder has been greatly increased. The air
cannot rush through the throttle body, intake manifold, cylinder head
port, and around the open intake valve fast enough to totally fill the
space created when the piston moves down rapidly. This is the most
common automotive vacuum supply source.

While performing vacuum testing, you should make sure that you are
not contributing to any vacuum leaks or disrupting any sensor
performance. With the engine idling, the following are general
indicators of engine performance:

Good Operations - An engine in good operating condition should have
a steady vacuum at about 16" to 22"Hg. Opening and closing
the throttle quickly will cause the needle to drop to 2 and then
come back to about 25.

Valve Problems - A 3 to 4 point intermittent drop of the needle denotes
valves are sticking. Also, a consistent vacuum drop could
indicate a burnt or leaky valve as the drop occurs when ever the
bad valve comes into operation. Worn valve guides admit air
which upsets the air/fuel mixture. Symptoms of worn valve
guides are a variable vacuum at idle of about 3"Hg, but steady
vacuum as rpm's increase. Weak valve springs will also have a
rapid fluctuation between 10" and 21"Hg at idle, but vacuum
becomes jumpy as rpm's increase. Any appreciable variation in
valve timing will produce a low reading.

Ignition Timing - If the ignition timing is off, the gauge will show a
steady, lower than normal reading.

Head Gasket Leak - Excessive vacuum variation at all rpm's could
indicate a bad head gasket (i.e., leaking compression). The
pointer will fluctuate between normal and a low reading. The
needle will drop sharply about 10"Hg from a normal reading
and return each time the defective cylinder or cylinders reach a
firing position. A Saab technician can confirm a head gasket
leak by performing a chemical test of the coolant fluid to test
for exhaust in the coolant.

ECU Testing

Before you do any testing on the system, you should make sure that all
ECU tests are done by probing the rear of the connector by peeling back
the rubber boot to gain access to the ECU connections. Also, the ECU
must never be unplugged while the ignition is on or within 60 seconds
of turning the ignition off. To be safe, you should avoid unplugging or
removing the ECU unless absolutely necessary. The reason for this is
that all ECUs are more or less sensitive to static electricity and, if
handled carelessly or incorrectly, they may be damaged so seriously
that they no longer work properly (by the way, dealer price is about
$500 for a rebuilt one).

Integrated Fault Diagnosis - Faults that only occur intermittently are
often difficult to find. The built-in memory in the LH 2.4 stores
information on such faults so that they can be identified and rectified.
When a fault has been detected, the CHECK ENGINE light on the
instrument panel will flash indicating that a fault has been detected.
Each fault has a special code consisting of a combination of short
flashes. The series of five flashes can be translated using the code
tables. The memory stores up to three faults. Once a fault has been
rectified, it may be necessary to erase the contents of the memory to
delete any additional codes for the same fault.

To pull the fault codes from the ECU memory, perform the following:

Using a jumper lead with a on-off switch, ground the single pin test
socket on the driver's side under the hood. The test socket
consists of three test attaching plugs - round, square w/4 plugs,
and L-shaped w/4 plugs. The grounding pin is attached to the
toe plug of the L-shaped w/4 plugs.

Switch on the ignition. The CHECK ENGINE light will now come on.

Set the switch to ON which provides ground to ECU pin 16 signaling
the ECU to send the fault codes. The CHECK ENGINE light
will now turn off.

Watch the CHECK ENGINE light carefully. After about 2.5 seconds,
it will flash briefly, signifying that the first code will now be
displayed. As soon as the light has flashed, move the grounding
switch that you have set-up immediately to the OFF position.

The first of three possible error codes will now be displayed by a
series of short flashes of the CHECK ENGINE light. Note
that the error code series starts and finishes with a long flash of
the CHECK ENGINE light. These long flashes are not part of
the code itself, but serve to indicate the beginning and end of
the code.

Each short flash of the CHECK ENGINE light is counted as a "1".
The sum of the short flashes indicates the digits number.
When the switch is set to OFF, the error code will be
flashed repeatedly. The next error code cannot be displayed
until the switch has been set to the ON position. Note that if
the test is run with the engine not running, the first code
displayed will be 12231 (no rpm signal).

To retrieve the next error code, set the switch to ON. After a short
flash of the CHECK ENGINE light, set the switch back to
the OFF position. The next error code will now be displayed
in a series of flashes.

Follow the same procedure to display the error code for the third
fault, if any. If no third fault has been detected or all the faults
have been fixed, the system will indicate this by a continuous
series of five long flashes (00000).

To delete the memory contents, set the switch to ON. After three
short flashes, set the switch to OFF. Note that the memory
contents cannot be deleted until all codes have been read and
code 00000 has been displayed.

Here's how to check stuff... assuming you already know how to retrieve fault
codes.

For these tests, you ground the jumper BEFORE turning on the ignition. DON'T
start the engine. When the check engine light (CEL) flashes once, open the
jumper and listen for the fuel pump to run for about 1 second.

Ground the jumper till the CEL flashes once, then open it for the next test.
After you're done with each test, ground the jumper till the CEL flashes
once, just like you're trying to read the next fault code. Each test, in this
order, displays a code like the faults: